If this a loan from employer to employee, then it could be considered a beneficial loan, especially if loan payments are deducted from your salary.
Guidance can be found on this at
Beneficial loan arrangements (480: Chapter 17)
Peer to peer lending is an alternative investment providing opportunities for individuals to lend directly to other people or businesses without using a bank.
Peer to peer lending
The interest received from peer to peer loans is taxable in the same way as any other interest received. Interest payments received from peer to peer loans may be paid either with or without deduction of tax. If someone receives interest without deduction of tax, they will need to notify HMRC of the income and to pay the correct amount of tax.